Cleanup/Documentation: Add/move comments for asset files

Adds some basic high-level explanations for editor/UI level asset APIs.
Also moves one such comment from the source file to the header file,
so it's in the same file as other API comments.

source/blender/editors/asset/ED_asset_catalog.h

@@ -16,6 +16,8 @@
 
 /** \file
  * \ingroup edasset
+ *
+ * Supplement for `ED_asset_catalog.hh`. Part of the same API but usable in C.
  */
 
 #pragma once

source/blender/editors/asset/ED_asset_catalog.hh

@@ -16,6 +16,11 @@
 
 /** \file
  * \ingroup edasset
+ *
+ * UI/Editor level API for catalog operations, creating richer functionality than the BKE catalog
+ * API provides (which this uses internally).
+ *
+ * Note that `ED_asset_catalog.h` is part of this API.
  */
 
 #pragma once

source/blender/editors/asset/ED_asset_filter.h

@@ -16,6 +16,8 @@
 
 /** \file
  * \ingroup edasset
+ *
+ * Functions for filtering assets.
  */
 
 #pragma once

source/blender/editors/asset/ED_asset_handle.h

@@ -16,6 +16,12 @@
 
 /** \file
  * \ingroup edasset
+ *
+ * Asset-handle is a temporary design, not part of the core asset system design.
+ *
+ * Currently asset-list items are just file directory items (#FileDirEntry). So an asset-handle
+ * just wraps a pointer to this. We try to abstract away the fact that it's just a file entry,
+ * although that doesn't always work (see #rna_def_asset_handle()).
  */
 
 #pragma once

source/blender/editors/asset/ED_asset_temp_id_consumer.h

@@ -16,6 +16,11 @@
 
 /** \file
  * \ingroup edasset
+ *
+ * API to abstract away details for temporary loading of an ID from an asset. If the ID is stored
+ * in the current file (or more precisely, in the #Main given when requesting an ID) no loading is
+ * performed and the ID is returned. Otherwise it's imported for temporary access using the
+ * `BLO_library_temp` API.
  */
 
 #pragma once

source/blender/editors/asset/intern/asset_handle.cc

@@ -16,12 +16,6 @@
 
 /** \file
  * \ingroup edasset
- *
- * Asset-handle is a temporary design, not part of the core asset system design.
- *
- * Currently asset-list items are just file directory items (#FileDirEntry). So an asset-handle is
- * just wraps a pointer to this. We try to abstract away the fact that it's just a file entry,
- * although that doesn't always work (see #rna_def_asset_handle()).
  */
 
 #include <string>